Fix #11. Throw when move path is descendent of from

lib/jsonPointer.js

@@ -6,6 +6,7 @@ exports.find = find;
 exports.join = join;
 exports.absolute = absolute;
 exports.parse = parse;
+exports.contains = contains;
 exports.encodeSegment = encodeSegment;
 exports.decodeSegment = decodeSegment;
 exports.parseArrayIndex = parseArrayIndex;
@@ -69,6 +70,10 @@ function parse(path) {
 	return split(path).map(decodeSegment);
 }
 
+function contains(a, b) {
+	return b.indexOf(a) === 0 && b[a.length] === separator;
+}
+
 /**
  * Decode a JSON Pointer path segment
  * @see http://tools.ietf.org/html/rfc6901#page-3

lib/patches.js

@@ -284,6 +284,10 @@ function commuteRemove(remove, b) {
  * @param {object} change move operation
  */
 function applyMove(x, change) {
+	if(jsonPointer.contains(change.path, change.from)) {
+		throw new InvalidPatchOperationError('move.from cannot be ancestor of move.path');
+	}
+
 	var pto = find(x, change.path);
 	var pfrom = find(x, change.from);
 

test/jsonPatch-test.js

@@ -2,6 +2,7 @@ var buster = require('buster');
 var assert = buster.referee.assert;
 var refute = buster.referee.refute;
 
+var patches = require('../lib/patches');
 var jsonPatch = require('../lib/jsonPatch');
 var InvalidPatchOperationError = require('../lib/InvalidPatchOperationError');
 
@@ -109,6 +110,14 @@ buster.testCase('jsonPatch', {
 			var result = jsonPatch.apply([{ op: 'move', path: '/y', from: '/x' }], a);
 			assert.equals(result.y, 1);
 			refute.defined(result.x);
+		},
+
+		'=>should not allow moving to ancestor path': function() {
+			var from = '/a/b/c';
+			var to = '/a/b';
+			assert.exception(function() {
+				patches.move.apply({ a: { b: { c: 1 }}}, { op: 'move', from: from, path: to });
+			});
 		}
 	},